Problems with Qt 4.8.5 and MinGW/GCC 4.8.1 - qt

Question

I just made a clean install of the following tools on Windows 7:
MinGW / GCC 4.8.1
Qt 4.8.5
Qt Creator 2.8.1
In the PATH there is: C:\Qt\4.8.5\bin;C:\Qt\4.8.5\include;C:\Qt\4.8.5\lib;C:\MinGW\bin;
1) I read the warning about the fact that Qt 4.8 needs GCC 4.6. I ignored it, using GCC 4.8.1. So this could be an issue.
2) I successfully installed Qt Creator. I successfully built the default Qt GUI application. When launched I get the error: "The program has unexpectedly finished." Debugging I get a segmentation fault before entering main(), in the qatomic_i386.h file, in the QBasicAtomicInt::deref() member function.
If I build a cmake based console application, everything is fine.
3) If I build a previous Qt cmake based project (either from the command line or from Qt Creator), this is what I get (out of tree build):
The first time I run cmake:
MyPrj-build>cmake -G "MinGW Makefiles" ..\MyPrj
CMake Error at C:/Program Files (x86)/CMake 2.8/share/cmake-2.8/Modules/CMakeMinGWFindMake.cmake:20 (message):
sh.exe was found in your PATH, here:
C:/Program Files (x86)/Git/bin/sh.exe
For MinGW make to work correctly sh.exe must NOT be in your path.
Run cmake from a shell that does not have sh.exe in your PATH.
If you want to use a UNIX shell, then use MSYS Makefiles.
Call Stack (most recent call first):
CMakeLists.txt:6 (PROJECT)
CMake Error: Error required internal CMake variable not set, cmake may be not be built correctly.
Missing variable is:
CMAKE_C_COMPILER_ENV_VAR
CMake Error: Error required internal CMake variable not set, cmake may be not be built correctly.
Missing variable is:
CMAKE_C_COMPILER
CMake Error: Could not find cmake module file:S:/MyPrj/MyPrj-build/CMakeFiles/2.8.11.2/CMakeCCompiler.cmake
CMake Error: Error required internal CMake variable not set, cmake may be not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILER_ENV_VAR
CMake Error: Error required internal CMake variable not set, cmake may be not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILER
CMake Error: Could not find cmake module file:S:/MyPrj/MyPrj-build/CMakeFiles/2.8.11.2/CMakeCXXCompiler.cmake
CMake Error: CMAKE_C_COMPILER not set, after EnableLanguage
CMake Error: CMAKE_CXX_COMPILER not set, after EnableLanguage
-- Configuring incomplete, errors occurred!
The second time:
S:\MyPrj\MyPrj-build>cmake -G "MinGW Makefiles" ..\MyPrj
-- The C compiler identification is GNU 4.8.1
-- The CXX compiler identification is GNU 4.8.1
-- Check for working C compiler: C:/MinGW/bin/gcc.exe
-- Check for working C compiler: C:/MinGW/bin/gcc.exe -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: C:/MinGW/bin/g++.exe
-- Check for working CXX compiler: C:/MinGW/bin/g++.exe -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
CMake Error at C:/Program Files (x86)/CMake 2.8/share/cmake-2.8/Modules/FindQt4.cmake:1382 (message):
Found unsuitable Qt version "" from NOTFOUND, this code requires Qt 4.x
Call Stack (most recent call first):
CMakeLists.txt:12 (FIND_PACKAGE)
-- Configuring incomplete, errors occurred!
Is it normal to have these different behaviours in the first and second cmake run?
Why cannot the system find Qt4?
Are these three issues dependent on each other?

Answer 1

How did you "install" your Qt? The only way of "installing" it in your case is to build it from the sources. Generally, you need to use the same compiler to compile Qt as you use to compile your Qt-using project. Some C++ compiler version mismatches might work, but you've just shown that your combination doesn't.